In recent years, substitution of soft polyolefin resins for soft polyvinyl chloride resins is investigated because of an endocrine problem and problems such as generating dioxin in burning.
Disclosed is a process in which soft polyolefin materials having a high transparency can be produced in a good morphology (for example, Japanese Registered Patent No. 3240589), but when they are used for films and wraps, the transparency equivalent to those of polyvinyl chloride resins is not obtained.
Further, disclosed is a process for producing soft materials having a high transparency in which a metallocene catalyst is used (for example, Japanese Unexamined Patent Application Laid-Open No. 95820/2000), but because a polymer produced in a solution used in the production is completely dissolved, a viscosity of the solution goes up, and a concentration of the polymer in the solution can not be raised, so that the productivity is low.
The present invention relates to a process for producing a propylene-ethylene block copolymer having a high transparency and a low elastic modulus in a good morphology and a propylene-ethylene block copolymer obtained by the above process.